Vintage Dress~Or is it a Coat??

I found this great dress at a local thrift~Then once i got it home,the more i looked at it i got the feeling of old style equestrian,,with the tight waist & pouffy gathered pocket..

Almost a full zip,, i was thinking maybe it was a covering/coat for a dress???

NO labels whatsoever~Feels almost like a windbreaker nylon,,but softer with a slight sheen to it..maybe a silk crepe??

Has anyone seen or have something like this? Thanks in advance